Consequences of inbreeding for the cowpea seed beetle, Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Abstract

Inbreeding is said to reduce vigour and fitness. It may also determine how a population responds to selection. Local populations of Callosobruchus maculatus, the cowpea seed beetle, are established annually from small numbers of founders and the species has been distributed to many parts of the world where isolated populations may have been founded by very small numbers of individuals. After more than 20 generations of inbreeding, inbred lines have been shown to diverge from a common ancestral stock in similar directions with respect of some variables such as developmental speed, but haphazardly in respect of other parameters such as male weight. The respective roles of drift and of selection as effective evolutionary forces in inbred lines are discussed in the light of these results. It is argued that some intraspecific differences in C. maculatus may be explained as a product of periodic inbreeding, but that the process does not impair the ability to adapt to local conditions so contributing to the status of the species as a pest of international importance.

Inbreeding-environment interactions for fitness: complex relationships between inbreeding depression and temperature stress in a seed-feeding beetle

“…There was no difference between the sexes in the magnitude of inbreeding depression on development time or adult body mass (non-significant sex 9 treatment interaction for d; development time: F 1,678 = 0.00, P = 0.96; mass: F 1,678 = 0.04, P = 0.84), in contrast to results found for a different population of C. maculatus (Tran and Credland 1995).…”

“…Similarly, inbreeding has been shown to affect female, but not male, adult body size (Tran and Credland 1995). Inbreeding also negatively affects female fecundity in both C. maculatus (Tran and Credland 1995) and its congener C. chinensis (Tanaka 1990(Tanaka , 1993.…”

“…Eggs from full-sib matings are 17-21% less likely to produce an adult offspring than eggs from outbred matings in C. maculatus . Inbred offspring that survive to sexual maturity develop more slowly-larval development time is extended by *5% ([1 day) (Tran and Credland 1995;Fox et al 2007). Inbreeding also affects adult lifespan of female, but not male, C. maculatus (Fox et al 2006;Fox and Stillwell 2009).…”

Inbreeding depression in development, survival, and reproduction in the adzuki bean beetle (Callosobruchus chinensis)

“…However, in these populations, the magnitude of inbreeding depression was not measured in terms of reproduction, which is a major fitness component during the adult stage. Evidence indicates inbreeding depression of reproduction in C. maculatus, as lines that have been inbred for many generations have reduced reproductive success (Tran and Credland 1995;Bilde et al 2009). Also in the adzuki bean beetle, C. chinensis, which is closely related and ecologically similar to C. maculatus, female fecundity declined after inbreeding was repeated for four generations (Tanaka 1990).…”

Effect of Inbreeding on Host Discrimination and Other Fitness Components in a Seed Beetle

“…Periods of inbreeding may be common in these stored-product pests, because populations in stores of grain legumes are often founded by small numbers of individuals that emerge from Þeld-infested or transported seeds Credland 1995, Semeao et al 2012). Beetle populations in both the Þeld and laboratory exhibit substantial inbreeding depression for such traits as larval survival and development time, adult body size and lifespan, and male and female reproduction (Tran and Credland 1995;Fox et al , 2007Fox et al , 2012. Inbreeding depression for some beetle traits (e.g., survival) increases with the stressfulness of the environment (Fox andReed 2010, Fox et al 2011).…”